Radio shielded enclosures



May '21, 1957 Filed Jan. 21, 1953 w. M. DUNN 2,793,245

RADIO SfiIELDEiD ENCLOSURES 2 Sheets-Sheet l INVENTOR. 1 WILLIAM M.-DUNNATTORNEY.

May 21, 1957 w. M. DUNN 2,793,245

7 RADIO SHIELDED ENCLOSURES "Filed Jan. 21, 1953 2 Sheets-Sheet 2WILLIAM M. DUNN ATTORNEY.

ited States Patent RADIO SHIELDED ENCLOSURES William M. Dunn,Philadelphia, Pa., assignor to Ace Engineering & Machine Co., Inc.,Philadelphia, Pa., a corporation of Pennsylvania Application January 21,1953, Serial No. 332,349

Claims. (Cl. 174-35) This invention relates to radio shielded enclosuresand it relates more particularly to such enclosures made of separablepanels which may be shipped in knocked down form, and secured to eachother at the desired locations to provide enclosures, the interior ofwhich will be shielded against stray radio waves, and in which testingof various electrical instruments may be done without interference fromsuch waves which otherwise would seriously affect the accuracy of themeasurements and the success of the tests. Shielded enclosures of thecharacter aforesaid are used in laboratories and in other places wherevarious types of tests are performed such, for example, as radiointerference measurements, radio frequency calibrations, radioinspection tests, testing equipment for measuring minute voltages andtesting various other devices and appliances. The purpose of suchenclosures is to intercept and dissipate stray radio waves which wouldotherwise be the cause of serious and annoying disturbances.

Heretofore, considerable difliculty has been experienced, in theconstruction of such radio shielded enclosures, in maintaining theproper electrical connections between the screening sheets of thevarious panels, and in preventing the bolts used for securing the panelsto each other from acting as antennae which pick up and transmitundesired radio waves to and from the interior of 'the enclosure.

The principal object of the present invention is to provide a novel formof radio shielded enclosure made of separate screening panels adapted tobe assembled and bolted together at the desired locations.

A further object of the invention is to provide an e11- closure of thecharacter aforesaid which will be relatively inexpensive yet quiteefficient for its intended purpose.

A further object of the invention is to pnovide an enclosure of thecharacter aforesaid in which any possibility of the connecting boltsacting as antennae will be eliminated without undue complication of thestructure.

A further object of the invention is to provide an enclosure of thecharacter aforesaid in which proper electrical connection of theshielding screens or plates of the various parts will be effectedinexpensively yet effectively.

The nature and characteristic features of the present invention will bemore readily understood from the following description, taken inconnection with the accompanying drawings forming a part hereof, inwhich:

Figure 1 is a perspective View of a radio shielded room embodying themain features of the present invention;

Fig. 2 is a fragmentary vertical sectional view of a portion of thestructure illustrating the manner of securing the vertical wall panelsto the floor shielding panels, the section being taken on the line 2-2of Fig. 1;

Fig. 3 is a fragmentary vertical sectional view of a portion of thestructure illustrating the manner of securing the top or ceiling panelsto the sidewall panels, the section being taken on the line 33 of Fig.1;

Fig. 4 is a fragmentary horizontal sectional view taken on the line 44of Fig. 1 illustrating the manner of securing the. side panels to eachother at intermediate points;

Fig. 5 is a horizontal sectional view, taken on the line 5-5 of Fig. 1,illustrating the manner of securing the door jam to the adjacent panelsand for establishing the necessary electrical connection of the metallicdoor parts when the door is closed; and

Fig. 6 is a perspective view of certain of the parts shown in separate-drelationship preparatory to the assembly thereof.

It should, of course, be understood that the description and drawingsherein are illustrative merely and that various modificationsand-changes may be made in the structure disclosed without departingfrom the spirit of the invention.

Referring to the drawings, in the particular embodiment of the inventiontherein shown, the sidewalls of the enclosure are made up of a series ofvertical screened panels secured to each other in a manner to bepresently explained.

Likewise, the ceiling is made up of a series of horizontally disposedscreened panels resting on and secured, in.a manner to be presentlyexplained, to the panels which make up the sidewalls.

Also, the floor is made up of a series of screened panels which areplaced on the primary floor 10 of the building in which. the shieldedenclosure is to be erected. The screened floor panels have superposedthereon a series of panels 11 preferably made of plywood which rest uponthe screened floor panels and provide the floor proper of the enclosure.

Each of the screened panels, whether the same is used for the sidewalls,ceiling or the screening floor panels, consists primarily of arectangular frame work comprising side strips 12, running lengthwise ofthe panels, connected at their ends by strips 13, running transverselyof the panels, and intermediate strips 14, also running transversely ofthe panels.

All the strips 12, 13 and 14, above described, are preferablyrectangular in cross-section with the exception of certain of thestrips, 12 or 13*, as the case may be, which are to be joined to theothers of adjoining panels at the vertical corners of the sidewalls,around the horizontal edges of the ceiling, and around the outer edgesof the floor at which places one of the abutting strips is recessed, asat 15, to receive the end or edge of the abutting panel.

The frame work of each of the panels, in each instance, is provided on:one face thereof with screening material 16, which preferably consistsof woven wire cloth of relatively fine mesh, although sheet material mayin some instances be used, for preventing the passage of radio waves tothe interior of the enclosure.

The screening material 16 is carried around outer edges of the strips atthe sides and ends of the respective panels, and into and across therecesses 15 where the same are employed.

The respective panels are secured to each other by means of bolts 17,the threaded ends of which engage complementally threaded pressureplates 18. Somewhat similar pressure plates 19 are also employed underthe heads of the bolts 17, but these pressure plates 19 are not threadedas are the plates 18 used at the threaded ends of the bolts.

The bolts 17 employed for securing the side strips 12 of the panels toeach other, as shown more particularly in Pig. 2 of the drawings, extendthrough said strips on the outside of the screening material 16 asshown.

Likewise, the bolts 17, which are used at the corner edges, that is tosay, where the top horizontal strips of the sidewall panels join themarginal edge strips of the ceiling, and where the vertical edge stripsof the end panel of one sidewall is joined to the vertical edge strip ofthe end panel of the adjacent sidewall, as shown in detail in Fig. ofthe drawing, are located, in each instance, outside of the respectiveplanes of the main screening cloth on the inner faces of the variouspanels. As hereinbefore'pointed out, considerable difficulty has beenexperienced in structures of this character to insure the properelectrical connections between the screening material of the variouspanels, which is essential for the proper prevention of the passage andreradiation of radio waves, and in many instances it was necessary toresort to soldering which was objectionable by reason of the annoyanceand difficulties encountered in soldering done at the place of erection,but this difficulty has been effectually overcome in the presentstructure by the tension of the bolts causing the abutting surfaces ofthe screen cloth 16 which is carried around on the outside of each ofthe members at the sides and ends of the panels, and also in therecesses 15 in certain of the members of the panel frame, to contacteach other efficiently.

It is also essential that the bolt members, even where the same are onthe outside of the screening cloth 16, be in electrical connectiontherewith, and this is insured by the use of the flanged bushings 20,shown more particularly in perspective in Fig. 6 of the drawings. Thesebushings 20 are forced through the screen cloth and into the holesprovided for the passage of the fastening bolts by means of a suitablepunch or mandrel (not shown), and when thus mounted, these bushings 20not only serve to prevent fraying of the screen cloth at the placeswhere the bolts pass through the strips of the panel frames and otherparts, but will also serve to prevent the bolts from acting as antennaeto carry radio waves into the interior of the enclosure.

However, in the erection of structures of this character, it isadvisable thatthe screening material of the screening panels of thefloor structure be so disposed that the screening material 16 is on thebottom surface adjacent the upper surface of the primary floor 10 of thebuilding in which the radio shielded enclosure is erected, as when sodisposed said screening material is better protected against damage andwear.

In this instance, the screening material 16 is carried entirely aroundthe end and edge strips of the screening floor panels, and one of thebushings 20 is also employed at the inner or threaded end of the bolt(see Fig. 2), whereby said bolts will be prevented from serving asantennae carrying any undesired waves into the enclosure notwithstandingsaid bolts extend entirely through from the outside to the inside of thescreening material.

The fioor proper is provided by the use of plywood panels 11 disposedover the bottom screening panels of the structure as indicated in Fig. 2of the drawings.

The door structure is shown in perspective in Fig. l, and in detail, inhorizontal section, in Fig. 5 of the drawings. At the place where thedoor is provided, in lieu of a screening panel at that point there areprovided side stiles 30 secured to the adjacent panels by bolts 17, theinner ends of which are threaded into pressure plates 18 which are, inthis instance, located in suitable recesses 31 provided in the members30 at the places where the bolts 17 are located.

The side stiles 30 as well as the top and bottom members of the doorframe are preferably covered by sheet metal 32 which is pressed intogood electrical contact with the screening material of the adjacentpanels by the tension of the bolts 17.

The door proper comprises a suitable frame work provided on one facethereof, with screening cloth 16 which may be disposed on either theinner or outer face, as preferred, and, here again, sheet metal may beused in lieu of the screening cloth if desired.

The members 33 of the frame work of the door proper are at leastpartially encased in sheet metal 34, extending over the screening cloth16, around the outer edge of the frame work of the door and partially onthe inner face of the frame work of the door. The sheet metal 34 may besecured on the inner face by means of metallic strips 35 which aresecured to the frame work of the door by screws 36, and likewise, thesheet metal 3 3- may be secured on the outer face of the door frame bymetal strips 37 and screws 38. The strips 37 are preferably ofsufficient width to overlap the opening between the edge of the door andthe adjacent door frame member 30.

The frame members 33 of the door proper are also each provided withcontact strips 39 and 40 respectively secured to the door by havingportions thereof extending under the strips 35 and 37. These contactstrips 39 and 40 are adapted to contact with the metallic casing 32which partially surrounds the door frame members 30, and therebyestablish an electrical connection between said casing 32 and the metalparts of the door proper.

The use of the metallic strips 39 and 49 in this manner will effectivelyprevent the passage of any radio waves through the crevices or openingswhich extend around the outer edges of the'door.

By the foregoing arrangement there is provided a radio shieldedenclosure of the knock down type which may be quickly assembled at thedesired place and which is so constructed and arranged as to effectivelyprevent the passage of stray radio waves to the interior thereof, andwhich is also so constructed and arranged that none of the parts thereofwill act as antenna to pick up and transmit undesired radio waves fromthe exterior to the interior of the structure.

Furthermore, the device is so constructed and arranged that thesame maybe readily dismantled and moved from place to place without loss of anyof the protective properties thereof. The use of the bushings 20 willalso serve to prevent fraying and displacement of the screening materialwhen the bolts are removed for any purpose.

I claim;

1. In a radio shielded enclosure including a plurality of separatelyconstructed panel frames each including lengthwise extending side stripsand transversely extending end strips, said side strips and end stripsconstituting marginal members, said panel frames each having radio wavescreening material on the inner face thereof, means for securing thepanels to each other and for electrically connecting the screeningmaterial of panels adjacent each other comprising the provision of anextending portion of the screening material for each panel on theportions thereof abutting the adjacent panels, bolts extending throughopenings in the marginal members of said panels and metallic bushingsengaging said screening material and extending into the holes throughwhich said bolts extend, said bushings each having a flanged portionextending over a portion of the screening material which it engages.

2. In a radio shielded enclosure comprising a plurality of separatelyconstructed panel frames each including lengthwise extending side stripsand transversely extending end strips, said side strips and end stripsconstituting marginal members, said panel frames each having radio wavescreening material on the inner face thereof, means for securing thepanels to each other and for electrically connecting the screeningmaterial of panels adjacent each other along corner edges of theenclosure comprising the provision at such locations of a recess in oneof the marginal members of one of said panels into which a marginalportion of another of said panels extends, the screening material ofeach panel having such recess being continued into said recess, and thescreening material of each of the other panels being continued aroundand over the abutting edge of said panel, bolts extending throughopenings in said marginal members, and metallic bushings engaging suchscreening material and extending into the holes through which said boltsextend, said bushings each having a flanged portion extending over aportion of the screening material which it engages.

3. In a radio shielded enclosure including a plurality of separatelyconstructed panel frames each including lengthwise extending side stripsand transversely extending end strips, said side strips and end stripsconstituting marginal members, said vertical wall panel frames eachhaving radio wave screening material on the inner face thereof, and aplurality of similarly constructed panel frames forming part of thefloor structure each having radio wave screening material on the lowerface thereof, the means for securing the floor panels to the verticalwall panels and for electrically connecting the screening material ofsaid panels to each other along the lower corner edges of the enclosurecomprising the provision of a recess in the lower marginal member ofeach of said vertical wall panels into which a marginal portion of oneof the floor panels extends, the screening material of each wall panelhaving such recess being continued into said recess, the screeningmaterial of the adjacent floor panel extending entirely around themarginal member thereof which is positioned within the recess of thewall panel, bolts extending through openings in said marginal members ofthe wall and floor panels, said bolts being in electrical connectionwith the portions of the screening material which extend around themarginal members of the floor panels, and metallic bushings engagingsaid screening material and extending into the holes through which saidbolts extend, said bushings each having a flange portion extending overa portion of the screening material which it engages.

4. The shielded enclosure of claim 1 further characterized by aplurality of panel frames forming part of the floor structure eachhaving radio wave screening material aifixed to said frame, and meansfor securing the floor panels to the vertical wall panels and forelectrically connecting the screening material of said panels to eachother along the lower corner portions of the enclosure, said meanscomprising the provision of screening material of the floor panelsextending entirely around the marginal members thereof and engagingportions of the screening material of the vertical wall panels.

5. The shielded enclosure of claim 1 further characterized by floorpanels secured to vertical wall panels and in which said bolts pass fromoutside the shielded enclosure to the inside thereof and are maintainedin electrical contact with portions of the screening material whichextend around the marginal members of said panels.

References Cited in the file of this patent UNITED STATES PATENTS1,744,004 Hunt Jan. 14, 1930 1,967,591 Proctor July 24, 1934 2,221,105Otto Nov. 12, 1940 2,405,987 Arnold Aug. 20, 1946 2,599,944 SalisburyJune 12, 1952 OTHER REFERENCES Rand et al.: Modern Plastics, Sept. 1951,page 105. (Copy in Se. Library.)

Publication I, ARRL Report No. 5-48. Specification and DesignCharacteristics for ARRL Screen-Room Model 1A and 1B. Published by U. S.Naval Air Development Center at Johnsville, Pa. Aug. 11, 1947. 174-354.

Publication II, NRL Report 3908. Measuring the Shielding Efliciency ofScreened Enclosures. Published by Naval Research Laboratory, Washington,D. C. Nov. 14, 1951. 20-2H.

Publication III, Blueprint No. E-l001 Screen Room, A. E. E. L. CellType, Semi-Portable, drawn March 26, 1948, U. S. Naval Air DevelopmentStation, Iohnsville, Pennsylvania, sheet 2 of 2 sheets. (Copy in Div.69, 174-354.)

